Electrode catheters have been in common use in medical practice for many years. They are used to stimulate and map electrical activity in the heart and to ablate sites of aberrant electrical activity. In use, the electrode catheter is inserted into a guiding sheath which has been positioned in a major vein or artery, e.g., femoral artery, and guided into a chamber of the heart. Within the chamber, the catheter is extended past a distal end of the guiding sheath to expose the mapping assembly. The catheter is maneuvered through movements so that the mapping assembly is positioned at the tubular region in the heart chamber. The ability to control the exact position and orientation of the catheter is critical and largely determines how useful the catheter is.
Steerable catheters are generally well-known. For example, U.S. Pat. No. Re 34,502 describes a catheter having a control handle comprising a housing having a piston chamber at its distal end. A piston is mounted in the piston chamber and is afforded lengthwise movement. The proximal end of the elongated catheter body is attached to the piston. A puller wire is attached to the housing and extends through the piston, through the catheter body, and into a tip section at the distal end of the catheter body. In this arrangement, lengthwise movement of the piston relative to the housing results in deflection of the catheter tip section. The design described in U.S. Pat. No. RE 34,502 is generally limited to a catheter having a single puller wire. If bi-directional deflection is desire, more than one puller wire becomes necessary.
Catheters adapted for on-plane bi-directional deflection are also known. A flat beam is normally provided to enable deflection on both sides of the beam sweeping a defined plane. Metal flat deflection beams with shape memory are preferred and typically used in combination with metal puller wires. With this arrangement, anchoring of the metal puller wire on the metal deflection beam can be readily accomplished by use of a metal ferrule that is crimped onto a distal end of a metal puller wire and resistance welded with a flat metal wire to form a T-bar which is then resistance welded to the beam. However, metal and stainless steel puller wires and especially those constructed of Nitinol can be costly and weakened when crimped thus making them prone to breakage. Moreover, a catheter using fiber-based puller members can provide users with a smoother “feel” when manipulating deflection of the catheter. Some fiber-based puller members can also withstand a higher pull force than metal puller wires.
Thus, there is a desire for a catheter that employs the combination of a metal deflection beam and fiber-based puller members and provides a structure by which the fiber-based puller members can be readily and securely anchored to the metal beam.